A remote manipulation arm uses a master arm and a slave arm, when working in a hostile medium in addition to mechanical transmission for connecting joints of the segments of the master arm to those of the slave arm in order to provide control over the movement of the master arm as imposed by an operator, so that it is reproduced by the slave arm. One end of the master arm is held by the operator and another end of the slave arm comprises a manipulation tool.
The remote manipulation arm is generally in a single piece with the master arm being directly connected to the slave arm so that mechanical transmission is continuous. A prior art design is disclosed in French Patent 2 667 532 using a slave arm without a master arm being controlled by a device with buttons or a similar implement, in which the controls are converted into electric signals delivered by a control system in which motors control the transmission of the slave arm according to these electric signals. This allows for control over the slave arm in a different more accurate manner. Another feature of this system is that the forces in the slave arm, due to gravity or to the undertaken work, are no longer transmitted to the operator. This reduces operator fatigue but, it should be noted that, on the contrary, it does not provide the operator with a “feel” proportional to that experienced by the tool for improving the quality of the control. So-called force feedback devices are added for producing the desired reactions in the master arm. No such reaction may be produced according to this U.S. Pat. No. 2,667,532.
Prior art remote manipulation arms generally have limited movements. In this way the pivoting movement of a tubular segment, a so-called crossing segment, engaged through a protective wall and mounted on rolling bearings, is reduced by having the master arm pivot upwards. This can only be performed by a small angle, as too high an elevation would no longer allow the operator to suitably hold the master arm and with the pivoting of the master arm accompanied with corresponding pivoting of the slave arm causing the weight to produce an antagonist moment to the elevation which hinders the operator. Counterweights reduce the pivoting moment but their action remains incomplete in practice. In spite of their possibilities, the slave arms are therefore associated with reduced work space and especially with a low height. The aforementioned patent does not find a remedy to this insufficiency. Instead, it suggests having the slave arm pivot by a transversely positioned cylinder which only authorizes a small motion angle.
The most important object of the subject invention is therefore to increase the possibilities of movement in a remote manipulation arm preferably by raising the level where the slave arm may be placed and without causing any difficulty to the operator.